Lecture Summary

Week 1- week 5

(Gums and stabilizers)

FOOD HYDROCOLLOIDS= A RANGE OF POLYSACCHARIDES AND PROTEINS
-GUMS', 'STABILIZERS'
Functions:
primary:

Thickening agent
Gelling or texturizing agents

Secondary:

Stabilisation of emulsion
Suspension of particulates
Control of cystallisation
Encapsulation
Formation of film

use<2%, if> 2%=very viscous

structure of hydrocolloid polymer

Factors affect gum properties

molecular weight
monosaccharide composition
type of chains
number of side chains
distribution of side chains

Main classes of Hydrocolloids

derivatives from exudation or sap of tree
extract from seed (Locust bean gum)
extract from seaweeds (carrageenan)
microbial gum (xanthan gum)
extract from tubers (konjac)
extract from plant parts (pectin)

Thermoreversible gelling agents
*Gel formed on heating or cooling and the process is reversible
eg: gelatin, agar, kappa-carrageenan, Iota-carrageenan, LM pectin, HPMC.

Thermally irreversible gelling agents

*heating will not form solution
eg: alginate, starch, konjac, HM pectin.

Pectin

derived from peel of citrus fruits, apple pomace, sugar beet, sunflower heads.
types of pectin---High methoxyl pectin (HMP), DE> 50%

High methoxyl pectin (HMP)

DE---58% to 75%
to form gel, soluble solid content 55-85%, pH 2.8-3.8. (e.g. jam and jellies)
ultrarapid/rapid set (DE as high as 77)---used in jam with whole fruits, to ensure uniform distribution of fruits particles.
slow set (DE~58) ---used in very acid fruits such as blackcurrant to avoid premature gelation.

Low methoxyl pectin (LMP)
- DE < 50% — two sub-groups: Conventional low methoxyl pectin (LMP) and Amidated low methoxyl pectin (ALMP)
- Form gels in the presence of Ca2+, with a low solids content & wide pH range (1-7) [but soluble solids can be up to 85%]
- LMP – less Ca2+ reactive than ALMP ⇒ used as a thickening agent in yoghurt fruit
- ALMP – very Ca2+ reactive ⇒ assist gelation in low sugar fruit preparations, e.g. low-sugar jams & jellies